Porsthetic knee components have long been known and used in the art. In order to prepare the femor and tibia for the components, it is necessary to make a series of cuts from these bones to conform to the size and shape of the prosthetic components. Generally these cuts are made by visual reliance on where cuts should be sometimes with the aid of simplified jigs and/or score lines. Such techniques are necessarily imprecise which limits the ability to provide the anatomically most desirable prosthetic knee.
Applicant's copending application, filed February 1982, the details of which are incorporated herein by reference thereto, describes such an anatomically desirable prosthetic knee system.
The aforenoted prosthesis is designed to reproduce anatomic movement of the knee without compromising stability. This prosthetic knee, as the natural knee, provides a "screw home" mechanism which increases stability in extension. As flexion proceeds, the femoral condyles initially roll posteriorly. Through asymmetric condylar and tibial compartments, the natural and changing axes of rotation are preserved, thereby preventing the development of abnormal tension in retained ligaments. When abnormal ligamentous tension develops, it either restricts flexion and increases shear stress at fixation interfaces and/or leads to eventual progressive ligament attenuation and joint instability. The design also allows natural internal and external rotation of the knee in flexion. Furthermore, contouring of the posterior margins of the tibial plateaus facilitates stability in flexion and provides a broad contact surface. The combination of these factors, which balance soft tissue elements in the joint, minimizes shear stress at the fixation interfaces, enhancing the potential for long term function of the replaced knee.
In order to make such prosthetic knee system feasible, the necessary bone cuts must be precisely accomplished. This, in turn, requires a set of proper instruments including guides and jigs. Such instruments should assure reproducibly accurate bone cuts, prosthetic seating, and lower limb alignment.